Various configured vibrators and vibrator rotors have been designed and developed for use in compacting or settling concrete. In one class of vibrators, the rotors have passages in which vanes slidably move as the rotor moves eccentrically in the vibrator housing. The vanes successively extend and engage the inner wall of the housing to form chambers between the inner wall of the housing and the outer surface of the rotor. The chambers receive fluid to create a pressure difference outside the rotor and to cause the eccentric movement of the rotor. In another class of vibrators, the rotor is not free running, rather, the rotor is journaled and supported in bearings in its movement within the vibrator housing. In another type of free rotor, the rotor acts like a turbine due to the velocity of pressurized fluid exiting jets formed in the rotor.
In still another type of free rotor, in which the present invention may be included, the rotor includes pistons placed in passages formed in the rotor. A chamber of pressurized fluid can be provided inside the rotor to create an unbalanced state to eccentrically move the rotor in the vibrator housing. In contrast to previously known vibrators of this type, the present invention incorporates pistons shaped like balls and dual-function valve ports, each of the valve ports both delivering pressurized fluid and exhausting fluid after it has done its work. In addition, the present invention incorporates novel means for preventing the separation of a portion from the housing after it has become worn and begins to break away from the housing. Such separation prevention means can be utilized in all classes of vibrators which may experience this type of failure mode.